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Interpretation ID: nht73-1.26

DATE: 04/23/73


TO: Hyster Company


TEXT: This is in reply to your letter of March 1, 1973, to Mr. J. E. Leveath of this Office, concerning the lighting requirements for special purpose dollies and trailers as manufactured by your company.

The first vehicle in question, which you identify as a helper dolly and(Illegible Word) on page 2 of your letter, would be classified as a trailer converter dolly for purposes of determining conformance to the Federal Motor Vehicle Safety Standards (FMVSS). As such, the vehicle is excepted from the lighting requirements specificed in FMVSS No. 108 (copy enclosed). The vehicle would, however, be subject to the applicable lighting requirements of the Bureau of Motor Carrier Safety (BMCS) regulations when it is towed alone (without an attached(Illegible Word) in interstate commorce.

The second and third vehicles in question, as shown on pages 3 and 4 of your letter, would be classified as trailers for purpose of determining conformance to FMVSS No. 108. As such, the vehicles must be equipped with lighting devices as specified in the standard. If the vehicles are 80 or more inches in overall width, front clearance lamps, installed as specified in Table II of the standard, are required. An interpretation of the term "overall width" is provided on page S 108-5 of the standard.

The requirements of FMVSS No. 108 are applicable to each new vehicle (truck, bus, trailer, etc.) as manufactured and offered for sale. The possibility that one vehicle may be operated in combination with another in no way alters the specified requirements. Vehicles operating in combination on the public highway are subject to regulations of the individual States and to BMCS regulations (for vehicles engaged in interstate commerce). BMCS regulations permit deactivation of lamps which are obscured when vehicles are operated in combination, but temporary removal of such lamps is prohibited (see 49 CFR, Sections 390.1 through 390.7, 393.14, 393.15, 393.25 and 393.26).

Should you desire additional information concerning the requirements of FMVSS No. 106, please do not hesitate to contact me. For further information on the BMCS regulations, I would suggest that you contact Mr. W. R. Fiste, Chief, Regulations Division, Bureau of Motor Carrier Safety, Federal Highway Administration, 400 Seventh Street, S. W., Washington, D. C. 20590.


MArch 1, 1973

Edward Leyseth National Traffic Safety Administration Department of Transportation

Dear Mr. Leyseth: We build heavy duty low bed trailers and related dollies and booster axles. I need some information concerning legal definitions of some of our vehicles and lighting equipment required by Federal Standard No. 108.

The first vehicle in question is a helper dolly, which is not a converter dolly because of load transfer and kingpin, but is similar in appearance and use (see page 2). What is the legal definition of this vehicle and what lighting equipment is required? What lighting is required by a converter dolly?

also build beam frame trailers designed for hauling large machinery, usually tracked, which straddle the frame to keep the load low and the trailer light (see page 3). Does this trailer require a front clearance light directly in front of the undercarriage? The trailer shown is a folding gooseneck type and is 5 ft. wide across the frame.

Next is a booster dolly, which is a hydraulically loaded trailing axle or axles articulated at the rear of the trailer. The frame comes to a point similar to tow type trailer tongue at the point of articulation (see page 4). What is the legal definition of this unit? Are front side marker and clearance lights required?

Also, can lights be temporarily removed when another vehicle in a combination prevents their visibility (e.g., the rear lights on a trailer are removed when a helper dolly is attached and replaced when the trailer is pulled alone)? Any information you could give me would be greatly appreciated.

Very truly yours,


Jim Glover,

Project Engineer